feat: check indentation in CI

.github/workflows/test.yaml

@@ -1,4 +1,4 @@
-name: Emacs Tests
+name: Test .el files
 
 on:
   push:
@@ -12,11 +12,10 @@ jobs:
       - name: Checkout source
         uses: actions/checkout@v3
 
-      - name: Download Emacs25 package
-        run: wget http://mirrors.kernel.org/ubuntu/pool/main/e/emacs25/emacs25-nox_25.2+1-6_amd64.deb http://mirrors.kernel.org/ubuntu/pool/main/e/emacs25/emacs25-bin-common_25.2+1-6_amd64.deb http://mirrors.kernel.org/ubuntu/pool/main/e/emacs25/emacs25-common_25.2+1-6_all.deb http://mirrors.kernel.org/ubuntu/pool/main/e/emacsen-common/emacsen-common_2.0.8_all.deb
-
-      - name: Install Emacs
-        run: sudo apt-get install --allow-downgrades ./emacs25-nox_25.2+1-6_amd64.deb ./emacs25-bin-common_25.2+1-6_amd64.deb ./emacs25-common_25.2+1-6_all.deb ./emacsen-common_2.0.8_all.deb
+      - name: Install Emacs 25
+        run: |
+          wget http://mirrors.kernel.org/ubuntu/pool/main/e/emacs25/emacs25-nox_25.2+1-6_amd64.deb http://mirrors.kernel.org/ubuntu/pool/main/e/emacs25/emacs25-bin-common_25.2+1-6_amd64.deb http://mirrors.kernel.org/ubuntu/pool/main/e/emacs25/emacs25-common_25.2+1-6_all.deb http://mirrors.kernel.org/ubuntu/pool/main/e/emacsen-common/emacsen-common_2.0.8_all.deb http://mirrors.kernel.org/ubuntu/pool/universe/c/compat-el/elpa-compat_29.1.4.4+dfsg-1_all.deb
+          sudo apt-get install --allow-downgrades ./emacs25-nox_25.2+1-6_amd64.deb ./emacs25-bin-common_25.2+1-6_amd64.deb ./emacs25-common_25.2+1-6_all.deb ./emacsen-common_2.0.8_all.deb ./elpa-compat_29.1.4.4+dfsg-1_all.deb
 
       - name: Install Just
         uses: extractions/setup-just@v1
@@ -27,3 +26,9 @@ jobs:
 
       - name: Run tests
         run: just test
+
+      - name: Check indentation
+        run: emacs --script scripts/indent-lisp-files.el
+
+      - name: Compare changes
+        run: git diff --exit-code

scripts/indent-lisp-files.el

@@ -0,0 +1,22 @@
+;;; indent-lisp-files.el --- call `indent-region' over all Lisp files -*- lexical-binding: t; -*-
+
+(require 'seq)
+(when (version< emacs-version "29.1")
+  (require 'compat)) ; file-name-parent-directory
+
+(defun .el-files-in (directory)
+  (seq-filter #'(lambda (path) (string-match "^.+\\.el$" path))
+    (directory-files directory)))
+
+(let*
+  ((root-path (file-name-parent-directory
+                (file-name-parent-directory load-file-name)))
+    (files (.el-files-in root-path))
+    (scripts (.el-files-in (concat root-path "/scripts"))))
+  (dolist (file (append files scripts))
+    (with-current-buffer (find-file-noselect file)
+      (setq indent-tabs-mode nil
+        lisp-indent-offset 2)
+      (indent-region (point-min) (point-max))
+      (save-buffer)
+      (kill-buffer (current-buffer)))))